The vast continental island of New Guinea and the islands that form an arc from its eastern end down toward the southeast (the Bismarck Archipelago, the Solomon Islands, the New Hebrides (the state of Vanuatu), and New Caledonia) represent a meeting ground of two cultural traditions and populations:
1. "Papuan". Papuans occupied the Sahul continent (now partly submerged) at least 40,000 years ago. As hunting-and-gathering peoples whose ways of life were adapted to tropical rain forest, they occupied the equatorial zone that, after sea levels rose at the end of the Pleistocene glacial period, became the vast island of New Guinea. Perhaps partly through indirect contact with developments in Southeast Asia, Papuan peoples developed one of the earliest agricultural complexes in the world (perhaps 9,000 years old, contemporaneous with the dawn of agriculture in the Middle East). Evidence indicates that they domesticated root crops and sugarcane and may have kept domestic pigs. By 5,000 years ago agricultural production in parts of the New Guinea Highlands was marked by systems of water control in agriculture and associated pig husbandry, both of which became intensified over subsequent millennia.
2. "Austronesian". About 4,000 years ago seafaring peoples bearing a Southeast Asian cultural tradition must have been moving in areas north of New Guinea; by 3,500 years ago they had occupied parts of the islands of the Bismarck Archipelago. Their presence is marked by the appearance of the distinctive pottery and associated tools and ornaments of shell that define the Lapita culture. They apparently spoke a language of the Austronesian family related to languages of the Philippines and the Indonesian archipelago. This early language is labeled Proto-Oceanic: from it are descended the languages of central and eastern Micronesia and Polynesia; the languages of the Solomons, Vanuatu, and New Caledonia; and many of the languages of coastal eastern New Guinea, adjacent islands, and much of the Bismarck Archipelago. The speakers of Proto-Oceanic, who had a maritime orientation and sophisticated seagoing technology, probably had a system of hereditary chiefs with political-religious authority and elaborate cosmogonies and complex religious systems that were not unlike those recorded in western Polynesia.
The Bismarck Archipelago east of New Guinea was already occupied by speakers of Papuan languages (whose earliest settlement has been dated to 30,000 years ago). The dark-skinned, woolly-haired populations anthropologists have classed as Melanesian that now occupy the Bismarck Archipelago and the arcs of islands extending to the southeast (the Solomons, Vanuatu, New Caledonia) represent the mixing of cultural traditions and biological heritages of Papuan and Austronesian peoples. The mixing may have taken place largely within the zone of the Bismarcks prior to the settlement of the islands to the southeast (although the exact process and relative contributions of these historical populations is debated). A great deal of economic interchange took place between a Southeast Asian complex based on root- and tree-crop cultivation and on maritime technology and the already well-developed Papuan agricultural and technological systems. It is probable that an interchange of other cultural traditions, from social organization to religion, took place as well. Some Austronesian-speaking communities (perhaps ones that retained their maritime orientation) appear to have remained relatively isolated from intermarriage and cultural interchange.
The Papuan languages include approximately 740 languages, used by about 3,000,000 speakers. SIL International (formerly known as the Summer Institute of Linguistics) works with language communities worldwide to facilitate language-based development through research, translation, and literacy. SIL lists the number of languages for Papua as 271, and for Papua New Guinea as 830.